Finance leases and other debt - Amended and Restated Loan and Security Agreement (Narrative) (Details) - USD ($)		3 Months Ended
	Dec. 04, 2023	Apr. 30, 2024	Jan. 31, 2024	Mar. 28, 2022	Mar. 27, 2022	May 05, 2020	Feb. 28, 2019
Debt Instrument [Line Items]
Debt		$ 2,877,000
Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount							$ 20,000,000
Financing arrangements
Debt Instrument [Line Items]
Debt		2,835,000	$ 3,124,000
Debt instrument, monthly payment		$ 123,000
Debt instrument, term		36 months
Effective interest rate		10.50%
Revolving Credit Facility | Second SVB Facility
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 50,000,000
Revolving Credit Facility | Third SVB Facility
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 100,000,000	$ 50,000,000
Stated interest rate (as a percent)		3.25%
Scheduled reduction in interest rate (as a percent)		0.50%
Annual fee amount		$ 250,000
Quarterly fee (as a percent)		0.15%
Line of Credit | Senior Secured Asset-based Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, term	5 years
Maximum borrowing capacity	$ 50,000
Quarterly fee (as a percent)	0.25%
Effective interest rate (as a percent)		8.30%
Debt issuance costs	$ 778,000
Line of Credit | Senior Secured Asset-based Revolving Credit Facility | Bridge Loan
Debt Instrument [Line Items]
Maximum borrowing capacity	5,000
Line of Credit | Senior Secured Asset-based Revolving Credit Facility | Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 5,000